IOS开发（58）之在 Block Object 中获取变量

1 前言
通过本次学习，我们就能够理解在 objective-c 方法和在 block objects 中获取变量的区别。

2 代码实例
main.m

 

[plain]
#import <foundation/foundation.h> 
#import "testdemo.h" 
int main(int argc, const char * argv[]) 
{ 
 
    @autoreleasepool { 
        testdemo *test = [[testdemo alloc] init]; 
//        [test log1]; 
//        [test simplemethod]; 
//        [test simplemethod2]; 
//        [test simplemethod3]; 
//        [test callcorrectblockobject]; 
//        [test simplemethod4]; 
//        [test log2]; 
//        [test scopetest]; 
        [test scopetest2]; 
    } 
    return 0; 
} 

#import <foundation/foundation.h>
#import "testdemo.h"
int main(int argc, const char * argv[])
{

    @autoreleasepool {
        testdemo *test = [[testdemo alloc] init];
//        [test log1];
//        [test simplemethod];
//        [test simplemethod2];
//        [test simplemethod3];
//        [test callcorrectblockobject];
//        [test simplemethod4];
//        [test log2];
//        [test scopetest];
        [test scopetest2];
    }
    return 0;
}
testdemo.h

 

[plain] view plaincopyprint?#import <foundation/foundation.h> 
 
@interface testdemo : nsobject 
 
@property (nonatomic, strong) nsstring *stringproperty; 
-(void)log1; 
- (void) simplemethod; 
- (void) simplemethod2; 
- (void) simplemethod3; 
- (void) callcorrectblockobject; 
- (void) simplemethod4; 
-(void)log2; 
- (void) scopetest; 
-(void) scopetest2; 
@end 

#import <foundation/foundation.h>

@interface testdemo : nsobject

@property (nonatomic, strong) nsstring *stringproperty;
-(void)log1;
- (void) simplemethod;
- (void) simplemethod2;
- (void) simplemethod3;
- (void) callcorrectblockobject;
- (void) simplemethod4;
-(void)log2;
- (void) scopetest;
-(void) scopetest2;
@end
testdemo.m

 

[plain]
#import "testdemo.h" 
 
@implementation testdemo 
 
@synthesize stringproperty; 
 
void (^independentblockobject)(void) = ^(void){ 
    nsinteger localinteger = 10; 
    nslog(@"local integer = %ld", (long)localinteger); 
    localinteger = 20; 
    nslog(@"local integer = %ld", (long)localinteger); 
}; 
 
-(void)log1{ 
    independentblockobject(); 
} 
//只读 
- (void) simplemethod{ 
    nsuinteger outsidevariable = 10; 
    nsmutablearray *array = [[nsmutablearray alloc] 
                             initwithobjects:@"obj1", 
                             @"obj2", nil]; 
    [array sortusingcomparator:^nscomparisonresult(id obj1, id obj2) { 
        nsuinteger insidevariable = 20; 
        nslog(@"outside variable = %lu", (unsigned long)outsidevariable); 
        nslog(@"inside variable = %lu", (unsigned long)insidevariable); 
        /* return value for our block object */ 
        return nsorderedsame; 
    }]; 
} 
//可该 
- (void) simplemethod2{ 
    __block nsuinteger outsidevariable = 10; 
    nsmutablearray *array = [[nsmutablearray alloc] 
                             initwithobjects:@"obj1", 
                             @"obj2", nil]; 
    [array sortusingcomparator:^nscomparisonresult(id obj1, id obj2) { 
        nsuinteger insidevariable = 20; 
        outsidevariable = 30; 
        nslog(@"outside variable = %lu", (unsigned long)outsidevariable); 
        nslog(@"inside variable = %lu", (unsigned long)insidevariable); 
        /* return value for our block object */ 
        return nsorderedsame; 
    }]; 
} 
//获得self 
- (void) simplemethod3{ 
    nsmutablearray *array = [[nsmutablearray alloc] 
                             initwithobjects:@"obj1", 
                             @"obj2", nil]; 
    [array sortusingcomparator:^nscomparisonresult(id obj1, id obj2) { 
        nslog(@"self = %@", self); 
        /* return value for our block object */ return nsorderedsame; 
    }]; } 
 
 
 
//无变化block object要获得 self需要传参数进去 
void (^correctblockobject)(id) = ^(id self){ 
    nslog(@"self = %@", self); 
}; 
- (void) callcorrectblockobject{ 
    correctblockobject(self); } 
 
 
 
//修改类属性 
- (void) simplemethod4{ 
    nsmutablearray *array = [[nsmutablearray alloc] 
                             initwithobjects:@"obj1", 
                             @"obj2", nil]; 
    [array sortusingcomparator:^nscomparisonresult(id obj1, id obj2) { 
        nslog(@"self = %@", self); 
        self.stringproperty = @"block objects"; 
        nslog(@"string property = %@", self.stringproperty); 
        /* return value for our block object */ 
        return nsorderedsame; 
    }]; 
} 
 
//在独立 block object 内部,你不能使用 dot notation 读写一个已声明属性,在这个场景中可以使用这个合成属性的 getter and setter 方法来代替 dot notation: 
void (^correctblockobject1)(id) = ^(id self){ nslog(@"self = %@", self); 
    /* this will work fine */ 
    [self setstringproperty:@"block objects"]; /* this will work fine as well */ 
    nslog(@"self.stringproperty = %@",[self stringproperty]); 
}; 
 
-(void)log2{ 
    correctblockobject1(self); 
} 
 
//当出现在内联 block objects 中,有一条非常重要的规则你必须记住:内联 block objects 在其词法区域 会为这些变量复制值。此处发生的事情是在执行 block 的地方 block object 自身一直有一个 integervalue 变量的只读复制。 
typedef void (^blockwithnoparams)(void); 
- (void) scopetest{ 
    nsuinteger integervalue = 10; 
    /*************** definition of internal block object ***************/ 
    blockwithnoparams myblock = ^{ 
        nslog(@"integer value inside the block = %lu", (unsigned long)integervalue); 
    }; 
    /*************** end definition of internal block object ***************/ integervalue = 20; 
    /* call the block here after changing the 
     value of the integervalue variable */ 
    myblock(); 
    nslog(@"integer value outside the block = %lu",(unsigned long)integervalue); 
} 
 
//可改变变量值测试 
-(void) scopetest2{ 
    __block nsuinteger integervalue = 10; 
    /*************** definition of internal block object ***************/ 
    blockwithnoparams myblock = ^{ 
        nslog(@"integer value inside the block = %lu", (unsigned long)integervalue); 
    }; 
    /*************** end definition of internal block object ***************/ integervalue = 20; 
    /* call the block here after changing the 
     value of the integervalue variable */ 
    myblock(); 
    nslog(@"integer value outside the block = %lu", 
          (unsigned long)integervalue); 
} 
@end 

#import "testdemo.h"

@implementation testdemo

@synthesize stringproperty;

void (^independentblockobject)(void) = ^(void){
    nsinteger localinteger = 10;
    nslog(@"local integer = %ld", (long)localinteger);
    localinteger = 20;
    nslog(@"local integer = %ld", (long)localinteger);
};

-(void)log1{
    independentblockobject();
}
//只读
- (void) simplemethod{
    nsuinteger outsidevariable = 10;
    nsmutablearray *array = [[nsmutablearray alloc]
                             initwithobjects:@"obj1",
                             @"obj2", nil];
    [array sortusingcomparator:^nscomparisonresult(id obj1, id obj2) {
        nsuinteger insidevariable = 20;
        nslog(@"outside variable = %lu", (unsigned long)outsidevariable);
        nslog(@"inside variable = %lu", (unsigned long)insidevariable);
        /* return value for our block object */
        return nsorderedsame;
    }];
}
//可该
- (void) simplemethod2{
    __block nsuinteger outsidevariable = 10;
    nsmutablearray *array = [[nsmutablearray alloc]
                             initwithobjects:@"obj1",
                             @"obj2", nil];
    [array sortusingcomparator:^nscomparisonresult(id obj1, id obj2) {
        nsuinteger insidevariable = 20;
        outsidevariable = 30;
        nslog(@"outside variable = %lu", (unsigned long)outsidevariable);
        nslog(@"inside variable = %lu", (unsigned long)insidevariable);
        /* return value for our block object */
        return nsorderedsame;
    }];
}
//获得self
- (void) simplemethod3{
    nsmutablearray *array = [[nsmutablearray alloc]
                             initwithobjects:@"obj1",
                             @"obj2", nil];
    [array sortusingcomparator:^nscomparisonresult(id obj1, id obj2) {
        nslog(@"self = %@", self);
        /* return value for our block object */ return nsorderedsame;
    }]; }

 

//无变化block object要获得 self需要传参数进去
void (^correctblockobject)(id) = ^(id self){
    nslog(@"self = %@", self);
};
- (void) callcorrectblockobject{
    correctblockobject(self); }

 

//修改类属性
- (void) simplemethod4{
    nsmutablearray *array = [[nsmutablearray alloc]
                             initwithobjects:@"obj1",
                             @"obj2", nil];
    [array sortusingcomparator:^nscomparisonresult(id obj1, id obj2) {
        nslog(@"self = %@", self);
        self.stringproperty = @"block objects";
        nslog(@"string property = %@", self.stringproperty);
        /* return value for our block object */
        return nsorderedsame;
    }];
}

//在独立 block object 内部,你不能使用 dot notation 读写一个已声明属性,在这个场景中可以使用这个合成属性的 getter and setter 方法来代替 dot notation:
void (^correctblockobject1)(id) = ^(id self){ nslog(@"self = %@", self);
    /* this will work fine */
    [self setstringproperty:@"block objects"]; /* this will work fine as well */
    nslog(@"self.stringproperty = %@",[self stringproperty]);
};

-(void)log2{
    correctblockobject1(self);
}

//当出现在内联 block objects 中,有一条非常重要的规则你必须记住:内联 block objects 在其词法区域 会为这些变量复制值。此处发生的事情是在执行 block 的地方 block object 自身一直有一个 integervalue 变量的只读复制。
typedef void (^blockwithnoparams)(void);
- (void) scopetest{
    nsuinteger integervalue = 10;
    /*************** definition of internal block object ***************/
    blockwithnoparams myblock = ^{
        nslog(@"integer value inside the block = %lu", (unsigned long)integervalue);
    };
    /*************** end definition of internal block object ***************/ integervalue = 20;
    /* call the block here after changing the
     value of the integervalue variable */
    myblock();
    nslog(@"integer value outside the block = %lu",(unsigned long)integervalue);
}

//可改变变量值测试
-(void) scopetest2{
    __block nsuinteger integervalue = 10;
    /*************** definition of internal block object ***************/
    blockwithnoparams myblock = ^{
        nslog(@"integer value inside the block = %lu", (unsigned long)integervalue);
    };
    /*************** end definition of internal block object ***************/ integervalue = 20;
    /* call the block here after changing the
     value of the integervalue variable */
    myblock();
    nslog(@"integer value outside the block = %lu",
          (unsigned long)integervalue);
}
@end
运行结果

2013-05-09 22:25:34.087 blockobjectparamtest[946:303] integer value inside the block = 20

2013-05-09 22:25:34.089 blockobjectparamtest[946:303] integer value outside the block = 20